Holddown systems utilizing compressively distorted elastomer bodies



F. HOLDDOWN QYSTEMS UTILI Feb. 10, 1970 K. HALL 3,494,554

ZING COMPRESSIVELY DISTORTED ELASTOMER BODIES 2 Sheets-Sheet 1 Filed Feb. 8, 1968 INVENTOR.

HALL

FRANK KENNETH Feb. 10,1970 Y F K HALL 3,494,554

nowbown SYSTEMS uTuIIziNG COMPRESSIVELY DISTORTED ELASTOMER BODIES Filed Feb. 8, 1968 2 Sheets-Sheet 2 I gt4 J 6 INVENTOR.

" FRANK KENNETH HALL BY 44. 4 Lug -4 T1 H515.

United States Patent 3,494,554 HOLDDOWN SYSTEMS UTILIZING COMPRES- SIVELY DISTORTED ELASTOMER BODIES Frank Kenneth Hall, Findlay, Ohio, assignor to The D. S. Brown Company, North Baltimore, Ohio, a corporation of Ohio Filed Feb. 8, 1968, Ser. No. 704,052 Int. Cl. E01b 9/62, 9/68 US. Cl. 238310 11 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The present invention concerns holddown systems particularly adapted to securely position a railroad rail on a support member. The invention particularly concerns the use thereof on rail supports such as concrete ties, concrete beds, metal superstructures, etc. It further pertains to other combinations wherein one member is to be held in position relative to another member and may be used in lieu of bolt connections, welded connections, etc.

Railroad rails traditionally have been mounted on wooden cross ties spaced at close intervals by the driving of railroad spikes into the ties with the head portion of the spike overlapping the base flange of the rail. This has been true of both on ground rail systems and above ground, or elevated rail systems. With the fairly recent advent of improvements in the structural strength of concrete, rail systems embodying concrete ties or concrete beds have awakened the interest of railroad designers. Concrete beds or ties require considerable less maintenance and have a longer useful life than do the traditional wooden ties.

The adaptation of rail systems to the use of concrete ties and concrete road beds, however, also require a departure from the traditional concept of holding the rail on the ties, i.e., by spikes being driven into the wooden ties. Holddown systems for rails on concrete ties and/or concrete road beds or metal superstructures have been developed in recent years. Known holddown systems embody heavy metal structures. Some utilize metal components in torsion stress as the force-exerting members. A specific object of the persent invention concerns improvements in rail holddown systems wherein the traditional, wooden tie concept is abandoned in favor of prestressed concrete ties and/or concrete road beds in on ground or elevated rail systems.

BRIEF SUMMARY OF THE INVENTION Briefly, the invention concerns holding systems in general, i.e., systems for holding one member relative to another comprising a first member, a second member contiguous thereto to be held in fixed position relative to said first member, and means for transmitting thrust between said members including a compressively deformed elastomer body having opposite substantially parallel faces exerting an outward elastic recovery thrust against said substantially parallel faces with lines of thrust forces in said compressively deformed member "ice being essentially at right angles to said faces. An exemplary use thereof comprise rail holddown systems wherein the railroad rails are secured by a series of holddown devices materially different from and considerably improved over the traditional railroad spike. A base member of such device is fixedly secured relative to a concrete bed or tie or to other structural systems supporting the rail, such as metal superstructures in the case of elevated rail systems. This base member may be a bar or bars impedded in and projecting from opposite sides of a concrete tie or may be a member bolted or otherwise attached to the road bed or superstructure. The system further embodies a holddown member having a foot or feet bearing downwardly on the upper face of the base flange. The pressure exerted thereby is of a relatively high magnitude, i.e., in the order of at least several hundred p.s.i. This pressure is provided by an elastomer pressure body positioned between the base member and the hold down member in a state which is distorted compressively from its normal, unstressed state whereby the elastic recovery thrust forces resulting from the compressive distortion exerts a pressure thrust force to relatively high magnitude, sufficient to secure the rail tightly on ties or other rail support members.

The elastomer pressure member is inserted in the holddown system on the construction site. As is well known, it is diflicult to insert an elastomer member in a highly compressed state. To facilitate such insertion, the elastorner member may be compressively distorted or flattened, whereafter its temperature is lowered sufilciently to immobilize or freeze the member in the compressed or flattened state when the compression force is removed. It is maintained at this temperature until it is inserted on the job in the holddown system. Upon thawing or warming, the elastomer body regains its elastic recovery property and recovers toward its normal shape, which is the shape of the elastomer member before compressive distortion and low temperature immobilization thereof. The holddown system is dimensioned so that the inserted elastomer member cannot recover fully its original or normal shape, whereby the elastomer member is in a partially compressed state when it exerts its thrust force through the pressure transmitting member and its foot on the base flange of the rail. Thereby, there exists in effect the elastomer member in 'a partially compressed state. Through the utilization of the elastic recovery force of said member in attempting to return it to its original or normal state, it functions as the pressure exerting body in the holddown system.

The elastomer member may also be compressed between opposing, preferably substantially parallel faces of a holddown system or the like by other means. For example, the elastomer member may be inserted in an uncompressed state, and one or more shims may be driven between the body and the contiguous face of the holddown member to compress the elastomer member. Alternatively, the holddown device may be made in separate parts and assembled on the job site in a manner whereby the elastomer member is compressed upon assembly. In the case of rail holddown systems, the holddown units may be mounted on the rail without the elastomer member, which is inserted later.

DESCRIPTION OF THE DRAWINGS Several preferred forms of the invention are illustrated in the drawings, wherein:

FIG. 1 is a perspective view of a fragment of a railroad rail mounted on a series of rail holddown devices adapted in turn to be secured to ties or other members of the rail supporting structure or road bed;

FIGS. 1A, 1B, and 1C are enlarged, perspective views of the pressure-imparting member, the elastomer block 3 in its normal, uncompressed state, and the elastomer block in its compressed, immobilized state, respectively;

FIG. 2 is a transverse section through a railroad rail showing the holddown system members in holding position against the base flange of the rail;

FIG. 3 is a side elevation, as viewed from section plane 33 of FIG. 2, of the pressure imparting member;

FIG. 4 is a side elevation of another embodiment of a holddown assembly in combination with a railroad rail and a concrete tie, the latter shown in fragment;

FIG. 5 is a view similar to FIG. 4 showing still a further embodiment;

FIG. 6 is a fragmentary side elevation of the embodiment of FIG. 4;

FIG. 7 is a diagrammatic view of opposed members with an uncompressed elastomer body between opposing substantially parallel faces with parallel lines marked on the end face of said body;

FIG. 8 is a similar diagrammatic view of the same combination with said body compressively distorted between said faces;

FIG. 9 is a side elevation of a further embodiment of a holddown member; and

FIG. 10 is a fragmentary cross-section of a still further embodiment utilizing a shim plate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The preferred embodiment of FIGS. 1-3 constitutes a holddown assembly wherein the assembly is attached to, as by bolts, a rail supporting structure, which may be a series of railroad ties, an elevated or on ground level railroad bed, or a series of cross structures such as steel structural members of an elevated, monorail or dual rail system. The rail 10 has the usual base flange 11. The base of the rail 10 may rest on rubber pads or cushions 12 which rest on the road bed 13 (or ties 14, e.g., FIGS. 4 and 5) or on a base plate such as plate 16 of the holddown assembly. The latter plate may rest on the road bed itself, on cross ties thereof, or on elevated superstructures. As shown in FIGS 13, the base plate 16 has a pair of rectangular holes 17 which receive the bottom portion of a holddown or mounting plate 18 having lips 19 overlying the edges of the holes 17. The base plate 16 and mounting plates 18 are bolted by bolts 20 to the underlying support structure 13.

Each holddown unit has an upwardly extending arm 21 carrying at its upper end a bar 22. The bar 22 is rigid with the arm 21 and the base plate 16 and projects from opposite sides thereof.

The pressure transmitting member 23 is a hollow member having an inverted U-shaped head portion 24 defining an axial, inverted U-passage 25. The head portion 24 fits over, and has a sliding relationship with, the rigid bar 22. Preferably, there is one pressure transmitting member on each side of the arm 21. The side faces of the bar 22 and the side walls of the inverted U-passage 25 are oriented so that the sliding movement is approximately perpendicular to the upper face of the base flange 11.

The remainder of the pressure transmission member 23 comprises a wider base segment 26 having a regular trapezoidal, axial passage 27 and a depending foot 28. As shown in FIG. 3, the front and rear edges 29 and 30 have an arcuate taper so that the flange contacting notch 31 of the foot member has a relatively small area. The purpose of tapering or narrowing toward the flange contacting notch is to increase the force per unit area of thrust of foot member 28 against the flange 11.

The pressure exerting member comprises an elastomer block or body 32 which is compressively distorted in the assembly of the rail with the holddown devices. Prior to inserting blocks 32 in the passages 25 between the lower face 34 of the bar 22 and the upper face 33 of the passage 27, the block 32 is distorted by compression into a flattened form. Such form may be the form 32a shown in FIG. 1C, i.e., as shaped of a dimension similar to but smaller than the cross section of the passage 27. It is inserted in the passage 27 in the distorted or compressed shape and thereafter allowed to recover via the elastic forces of the elastomer block or body toward its normal state, i.e., the shape it would assume without any compressive forces exerted thereon. In this elastic recovery, the elastomer body 32 presses against faces 34 and 33 and thus everts a downward thrust on the pressure transmitting member 23. This force is in turn transmitted through the foot 28 against the upper face of the base flange 11 to hold the rail securely in position.

As aforesaid, it normally would be diflicult to insert the compressively distorted, elastomer body 32 in the pressure transmitting member 23. To facilitate such insertion, it is preferred that the elastomer body 32 be compressively distorted in a flattened shape such as shown in FIG. 1C, and frozen or immobilized in this state. It is held at the freezing or low temperature immobilization until it is inserted in the passage 27. As the elastomer body 32 warms, its resilient properties are restored and it seeks to resume its shape prior to compressive dis tortion and freezing. In so doing, it becomes wedged between the bar 22 in the upper face 33, and thus exerts a downward thrust on the pressure transmitting member 23.

The terms freezing and thawing above, are nontechnical descriptions. In practice, the elastomer body 32 is formulated so that the elastomer composition will rigidity, through loss of elastic properties, at relatively low temperatures, i.e., in the order of 40 F. and below. The elastomers also should have good resistance to atmospheric deterioration in the presence of sunlight, atmospheric oxygen, and ozone, and should retain their elastic properties also at relatively high temperatures on the order of to F. The elastomer compositions useful for this purpose may be formulated from elastomers which crystallize at relatively low temperatures with the loss of elastic properties upon crystallization. Exemplary thereof are low crystallization neoprene elastomers. However, elastomers which are usually considered to be noncrystalline elastomers, e.g., natural rubber and most synthetic rubbers, can be immobilized or rigidified in the compressively distorted state at low temperatures in the order of 0 F. to 100 F. or even lower. The invention herein contemplates use of any natural or synthetic rubber composition wherein such low temperature immobilization can be attained. The selection of a particular elastomer composition will depend in part on the climate of the locale where the installation is made. In northern parts of the temperate zone, a low temperature immobilization of 30 F. or below is recommended. In the arctic zone, a low temperature immobilization of 60 F. or below is recommended, whereas in southern parts of the temperate zone and in the tropical zone 0 F. or below would be suitable. In each instance, the low temperature immobilization is selected so that it will not be reached and preferably not even closely approached under the coldest climate conditions of the particular locale.

The embodiment of FIGS. 1-3 is particularly adapted for use where the rails are supported on a bed or other support which will be adapted to, or can be constructed to, receive both or like attaching devices to hold the base plate 16 securely in position. In rail systems embodying pre-stressed concrete ties, holddown systems of the type shown in FIGS. 4-6 may be employed. In the embodiment of FIGS. 4 and 6, the pre-stressed rail or ties 14 are molded with a pair of bars 35 projecting from the front and rear faces 36 and 37. These bars have flat sides 38 and 39 for slidable accommodation of the flat sides of the inverted U-shape passage 40 of the head portion 41 of the pressure transmitting member 42. The pressure transmitting member 42 comprises a base 43 having a regular trapezoidal, axial passage 44 of the type previously described. The passage 44 receives the elastomer pressure transmitting member 32, which may be of the same type and shape as shown in FIGS. 1 and 2 in the normal state as well as in the compressed state. Upon elastic recovery of the compressed or flattened elastomer body 32, a downward thrust on the lower wall 45 is exerted when the elastomer body 32 makes its elastic recovery between the bar 35 and the wall 45. This downward thrust is transmitted through upwardly extending arms 46 having upper, hook segments 47, the ends 48 of which exert a downward holding thrust against the upper faces of the flange 11. As shown in FIGS. 4 and 6, four of the pressure transmitting members 42 are employed to secure the rail tightly on the upper face of the tie 14.

In the embodiment of FIG. 5, the structure and mode of operation is similar to that of FIG. 4 except that the pressure transmitting member 50 has a pair of upwardly extending arms 51 and 52 instead of a single arm. In this embodiment only two pressure transmitting members 50 are employed, one on each side of the tie 14. A single bar 53 extends transversely through the tie 14. By use of the dual arms 51 and 52, a pair of pressure transmitting members 50 may be employed, one on each side of the tie.

FIGS. 7 and 8 illustrate in diagrammatic form the action of the compressed elastomer body in exertion of thrust along lines of force between the substantially parallel faces between which said body is compressed. These lines of force are those which normally result from deflection or compression as distinguished from shear or torsion. For purposes of illustration, the member 60 is a member to be held fixedly relative to member 61. In relation to the rail holddown systems above described, member 60 corresponds to fixed bars 22, 35 or 53, and member 61 corresponds to pressure transmitting members 23-28, 42 or 50.

The elastomer member, e.g., a solid elastomer block 62, has thrust component lines 63 marked on an end face at equal intervals. These lines are at right angles to the opposing parallel faces 64 and 65 between which the block 62 is compressed. When the block 62 is compressed from its normal shape (FIG. 7), the elastomer, being an incompressible solid, flows, whereby its faces 66 and 67 in contact with faces 64 and 65 assume a greater area unless confined by structures precluding such flow (not shown). At the same time, the sides 68 and 69 bulge outwardly to some degree.

Based on these observations, component forces in compressed block 62 exert thrust at substantially right angles to the faces 64 and 65 at various amount of compression of block 62 between parallel faces whereby the elastic recovery forces in the compressed block are working directly against the faces 64 and 65.

In the embodiment of FIG. 9, the rail holddown member is adapted to be used to hold a rail in a manner similar to the embodiment of FIGS. 4 and 6. The base portion thereof comprises an open end, inverted U-base 70 with flanges 71 projecting from the lower, outer corners thereof. The fixed bar 72 is positioned in the upper part of open portion 73. A plate 74 fits over the open, lower side of the inverted U-base and is held therein by the engagement of flanges 75 with flanges 71. The plate 74 has a well 76 to seat the solid elastomer block 77, which in the assembly is under compressive distortion between the lower face of bar 72 and the bottom wall of well 76. The elastomer block 77 engages the holddown member downwardly relative to fixed bar 72 and thereby presses the end 78 of the hooked segment 79 downwardly against the base flange of the rail.

The elastomer block 77 may be inserted in the assembly by the compression-freezing technique heretofore described. In the alternative, a power tool may be used on the job site to press plate 74 tightly against the bottom of base 70 with the elastomer block 77 in position. In the course thereof, the block is compressively distorted, and

flanges 75 either snap over flanges 71 or the former may be formed by the power tool after the plate 74 is pressed tightly against the bottom of base 70.

FIG. 10 is a fragmentary cross section of a holddown member as illustrated in FIGS. l-3. Like numerals designate like parts. In this embodiment a shim 80 having a tapered, relatively sharp edge 81 is forced between the elastomer member 32 and the upper face 33 of the pressure transmitting member. This narrows the space between opposing faces 33 and 34 and compresses the elastomer member so that it, in the assembly shown, exerts a downward thrust on the pressure transmitting member.

Thus, in its broader concepts the invention herein provides a system for holding one member relative to another by a compressively distorted, solid elastomer body or block. The system embodies a first member and a second member to be held in fixed position relative to the first member. The system embodies substantially parallel, opposed faces against which the compressively distorted elastomer body is positioned with its opposite faces pressing against said opposed faces to give an elastic recovery thrust force urging said faces apart along lines of thrust force at right angles to said faces. This com bination utilizes the elastic recovery forces in the compressed elastomer body more effectively than would be the case if the elastomer body were subject to twisting. In the latter case, the torque elastic recovery forces in the twisted elastomer adopt a sine curve-like configuration. Such recovery forces are considerably less effective in terms of amount of elastic recovery thrust forces per unit of distortion or deformation of the elastomer body as compared against the thrust force orientation achieved by this invention.

The elastomer body may exert its thrust force directly against the second member to be held relative to the first member, or, as in the illustrated rail holddown systems, a thrust transmitting member may be provided between the first member and the second member. The opposed parallel faces in such cases are on the first member and the thrust transmitting member, the latter having contact means such as a foot of small area bearing against the second member to hold the latter relative to the first member. The thrust transmitting member preferably is mounted in the system for lineal movement at right angles to the substantially parallel faces.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the form herein disclosed being a preferred embodiment for the purpose of illustrating the invention.

What is claimed is:

1. A system for holding one member relative to another by a compressively distorted elastomer body comprising a first member, a second member contiguous thereto to be held in fixed position relative to said first member, a thrust transmitting member having a thrust transmitting segment, opposed, spaced, substantially parallel faces on said first member and said thrust transmitting segment, contact means on said thrust transmitting segment bearing against said second member, and an elastomer body compressively deformed between said opposed faces and having opposite, substantially parallel faces exerting an outward elastic recovery thrust against said opposed, substantially parallel faces with lines of thrust forces in said compressively deformed elastomer body being essentially at right angles to said faces.

2. A system as claimed in claim 1, and means mounting said thrust transmitting member for lineal movement at right angles to said faces.

3. A system as claimed in claim 1, wherein said contact means comprises a foot of small surface area bearing against said second member.

4. A rail holddown system comprising, in combination, a railroad rail having a flange extending along the base thereof, a support beneath said rail, a thrust transmitting holddown member bearing against the upper face of said flange, a fixed member, opposed, spaced, substantially parallel faces on said fixed member and said thrust transmitting holddown member, and a compressively distorted elastomer block having opposite, substantially parallel sides positioned between said opposed faces of said fixed member and said holddown member and exerting via its elastic recovery an elastic recovery thrust against said opposed faces to provide the pressure force pressing said holddown member tightly against said flange.

5. A rail holddown device as claimed in claim 4, wherein said elastomer pressure member comprises an elastomer body which has been compressively distorted from its normal, relaxed shape and immobilized at low temperature in the distorted state prior to positioning thereof between said faces, and, upon warming in said cavity, has recovered toward its normal shape to create and maintain said pressure force.

6. A rail holddown system comprising, in combination, a railroad rail having a flange extending along the base thereof, a support beneath said rail, a holddown member bearing against the upper face of said flange, a fixed member including a fixed, rigid member above said flange, said holddown member including a head portion with a cavity and foot depending therefrom, said fixed member being vertically slidably positioned in the upper portion of said cavity, and a compressively distorted elastomer pressure member being positioned in-the lower portion of said cavity beneath said fixed member and exerting via its elastic recovery a pressure force between said fixed member and the bottom of said cavity, thereby pressing said foot downwardly against said flange.

7. A rail holddown system as claimed in claim 6, wherein said support is a concrete tie and said fixed member is a bar fixedly supported above said flange.

8. A rail holddown system comprising, in combination, a railroad rail having a flange extending along the base thereof, a support beneath said rail, a holddown member bearing against the upper face of said flange, a fixed member including a fixed, rigid member below said rail, said holddown member including a head portion with a cavity, a pressure transmitting arm extending upwardly from said head portion, and a downwardly facing hooked end on said arm hooked around said flange with the terminal end of said hooked end bearing against the upper face of said flange, said fixed member being slidably positioned in the upper portion of said cavity, and a compressively distorted elastomer pressure member positioned in the lower portion of said cavity beneath said fixed member and exerting via its elastic recovery a pressure force between said fixed member and the bottom wall of said cavity, thereby pressing said hooked end downwardly against said flange.

9. A rail holddown system as claimed in claim 8, wherein said support is a concrete tie and said fixed member is a bar embedded in and projecting from said tie.

10. A combination embodying a structural member pressing against and holding a second member by lines of thrust force which comprises a fixed structural member having a substantially planar face, a second member having a substantially planar face opposite to and spaced from said first mentioned face, a third member restraining movement of said second member away from said first member, and a solid elastomer block compressively distorted between said faces and exerting a thrust force at right angles to said faces against said face of said second member and pressing the latter against said third member.

11. A system for holding one member relative to another by a compressively distorted elastomer body comprising a first member, a second member contiguous thereto to be held in fixed position relative to said first member, a thrust transmitting member having a cavity therein, said first member being received in said cavity, opposed, spaced, substantially parallel faces on said first member and said thrust transmitting member, contact means on said thrust transmitting member bearing against said second member to hold the later relative to said first member, and a compressively deformed elastomer body in said cavity and having opposite substantially parallel faces exterting an outward elastic recovery thrust against said opposed, substantially parallel faces in said system with lines of thrust forces in said compressively deformed member being essentially at right angles to said faces.

References Cited UNITED STATES PATENTS 3,080,120 3/1963 De Turk 23'82:83 3,351,283 11/1967 Paasche et al. 238283 ARTHUR L. LA POINT, Primary Examiner R. A. BERTSCH, Assistant Examiner US. Cl. X.R. 238338, 349, 283 

